I don't know of any instances of SSL certificates being subverted in the way described by the GP, but there are instances of phishing sites using correct-looking certificates, such as http://blog.washingtonpost.com/securityfix/2006/02/the_new_face_of_phishing_1.html
"By what other method do you suggest that I prove to my satisfaction that when I go to www.mybank.com.au that I am actually at mybank's website"
Not very easily, but you can use two factor authentication to make sure that even if scammers find out the static username, password, and whatever, it's useless without a second bit of information generated by an electronic device. So the device generates a pin number which is based on time, or generated in a sequence. I have used Cryptocards in the past - they can generate a 7 digit pin number which is valid for one time only - the server knows the order that the card should generate the pin and it can be easily tied into existing infrastructure using by authing using RADIUS. Some UK banks have sent out devices which you need to insert the debit card into in order to generate the code. It's far less likely that the scammer is going to have the debit card, *and* the electronic device, *and* the static username/password.